Abstract
Magnetic susceptibility measurements have been made of the effect of applying a field on the critical divergence of the parallel susceptibility of the dilute antiferromagnets MncZn1-cF2 (c=0.45 and 0.6). The diverging susceptibility at the Neel temperature under an extremely weak external field, which originates from the coupling between uniform and staggered fluctuations, is suppressed with increasing magnetic field. This and the appearance of the remnant magnetisation below the Neel temperature suggest that the phase transition in these systems is destroyed by the induced random magnetic fields and the system splits into micro-domains.